This invention relates to improvements in fuse strips for electric circuits, the strips being designed to interrupt the flow of current in the event of overload current or short circuit current. Fuse strips are known in the art and are generally enclosed in an insulating cylindrical cartridge and are connected to two conductive caps closing the ends of said insulating cartridge.
The known fuse strips are usually provided with a transverse row of juxtaposed apertures that delimits short reduced cross section elements or necks which are designed to melt under overload or short circuit current.
It is also known in the art to longitudinally space two transverse rows of said apertures so as to define a narrow transverse band therebetween. A low melting point alloy is poured on this band for forming with the copper material of the fuse strip a low melting point eutectic alloy. This latter arrangement is used particularly for ensuring an exact interruption of the fuse strips in the case of overload currents.
In the above discussed fuse strips, two main drawbacks are present. One drawback consists in the fact that the usual apertures on the transverse rows of the fuse strips are so shaped that the piercing punches, which are used to form them, rapidly wear and have to be changed frequently.
The other drawback consists in the fact that the band supporting the low melting point alloy, on account of the prior art apertures, presents an irregular width, so that said alloy may not be poured in a line of regular width. Moresaid said alloy, in the step of pouring and in the step of interrupting the fuse, has a tendency to run out of said band, so that the exact point of interruption is varied from one fuse strip to another, and consequently it is about impossible to repeat on an electrical circuit the same characteristics of the interruption.